The objective of this study is to assess the blood pressure lowering effect of a single 300 mg oral dose of SR 49059 in African American and Caucasian hypertensive patients before, during, and after an hypertonic saline infusion. Based on pharmacology and both acute toxicology (LD0>2g/kg) and the 4-week repeated administration studies, and on preliminary safety data from the first single ascending oral dose tolerability trial, a minimal effective dose of 300 mg of SR 49059 is considered to be safe to be administered to humans. To date 6 subjects have completed the study. This is a single-dose, cross-over double blind study and all analyses will be carried out at the end of the study when the code is broken.